Polymeric conductor donor and transfer method

ABSTRACT

The present invention relates to a donor laminate for transfer of a conductive layer comprising at least one electronically conductive polymer on to a receiver, wherein the receiver is a component of a device. The present invention also relates to methods pertinent to such transfers.

CROSS-REFERENCE TO RELATED APPLICATION

This is a Divisional of application Ser. No. 10/969,889, filed Oct. 21,2004.

FIELD OF THE INVENTION

The present invention relates to a donor laminate for transfer of aconductive layer comprising at least one electronically conductivepolymer on to a receiver, wherein the receiver is a component of adevice. The present invention also relates to methods pertinent to suchtransfers.

BACKGROUND OF THE INVENTION

Transparent electrically-conductive layers (TCL) of metal oxides such asindium tin oxide (ITO), antimony doped tin oxide, and cadmium stannate(cadmium tin oxide) are commonly used in the manufacture ofelectrooptical display devices such as liquid crystal display devices(LCDs), electroluminescent display devices, photocells, solid-stateimage sensors, electrochromic windows and the like.

Devices such as flat panel displays, typically contain a substrateprovided with an indium tin oxide (ITO) layer as a transparentelectrode. The coating of ITO is carried out by vacuum sputteringmethods which involve high substrate temperature conditions up to 250°C., and therefore, glass substrates are generally used. The high cost ofthe fabrication methods and the low flexibility of such electrodes, dueto the brittleness of the inorganic ITO layer as well as the glasssubstrate, limit the range of potential applications. As a result, thereis a growing interest in making all-organic devices, comprising plasticresins as a flexible substrate and organic electroconductive polymerlayers as an electrode. Such plastic electronics allow low cost deviceswith new properties. Flexible plastic substrates can be provided with anelectroconductive polymer layer by continuous hopper or roller coatingmethods (compared to batch process such as sputtering) and the resultingorganic electrodes enable the “roll to roll” fabrication of electronicdevices which are more flexible, lower cost, and lower weight.

Electronically conductive polymers have recently received attention fromvarious industries because of their electronic conductivity. Althoughmany of these polymers are highly colored and are less suited for TCLapplications, some of these electronically conductive polymers, such assubstituted or unsubstituted pyrrole-containing polymers (as mentionedin U.S. Pat. Nos. 5,665,498 and 5,674,654), substituted or unsubstitutedthiophene-containing polymers (as mentioned in U.S. Pat. Nos. 5,300,575,5,312,681, 5,354,613, 5,370,981, 5,372,924, 5,391,472, 5,403,467,5,443,944, 5,575,898, 4,987,042, and 4,731,408) and substituted orunsubstituted aniline-containing polymers (as mentioned in U.S. Pat.Nos. 5,716,550, 5,093,439, and 4,070,189) are transparent and notprohibitively colored, at least when coated in thin layers at moderatecoverage. Because of their electronic conductivity these polymers canprovide excellent process-surviving, humidity independent antistaticcharacteristics when coated on plastic substrates used for photographicimaging applications (vide, for example, U.S. Pat. Nos. 6,096,491;6,124,083; 6,190,846;)

EP-A-440 957 describes a method for preparing polythiophene in anaqueous mixture by oxidative polymerization in the presence of apolyanion as a doping agent. In EP-A-686 662 it has been disclosed thathighly conductive layers of polythiophene, coated from an aqueouscoating solution, could be made by the addition of a di- or polyhydroxyand/or a carbonic acid, amide or lactam group containing compound in thecoating solution of the polythiophene.

Many miniature electronic and optical devices are formed using layers ofdifferent materials stacked on each other. These layers are oftenpatterned to produce the devices. Examples of such devices includeoptical displays in which each pixel is formed in a patterned array,optical waveguide structures for telecommunication devices, andmetal-insulator-metal stacks for semiconductor-based devices. Aconventional method for making these devices includes forming one ormore layers on a receiver substrate and patterning the layerssimultaneously or sequentially to form the device. In many cases,multiple deposition and patterning steps are required to prepare theultimate device structure. For example, the preparation of opticaldisplays may require the separate formation of red, green, and bluepixels. Although some layers may be commonly deposited for each of thesetypes of pixels, at least some layers must be separately formed andoften separately patterned. Patterning of the layers is often performedby photolithographic techniques that include, for example, covering alayer with a photoresist, patterning the photoresist using a mask,removing a portion of the photoresist to expose the underlying layeraccording to the pattern, and then etching the exposed layer.

Coated layers of organic electroconductive polymers can be patternedinto electrode arrays using different methods. The known wet-etchingmicrolithography technique is described in WO97/18944 and U.S. Pat. No.5,976,274 wherein a positive or negative photoresist is applied on topof a coated layer of an organic electroconductive polymer, and after thesteps of selectively exposing the photoresist to UV light, developingthe photoresist, etching the electroconductive polymer layer and finallystripping the non-developed photoresist, a patterned layer is obtained.In U.S. Pat. No. 5,561,030 a similar method is used to form the patternexcept that the pattern is formed in a continuous layer of prepolymerwhich is not yet conductive and that after washing the mask away theremaining prepolymer is rendered conductive by oxidation. Such methodsthat involve conventional lithographic techniques are cumbersome as theyinvolve many steps and require the use of hazardous chemicals.

EP-A-615 256 describes a method to produce a pattern of a conductivepolymer on a substrate that involves coating and drying a compositioncontaining 3,4-ethylenedioxythiophene monomer, an oxidation agent, and abase; exposing the dried layer to UV radiation through a mask; and thenheating. The UV exposed areas of the coating comprise non-conductivepolymer and the unexposed areas comprise conductive polymer. Theformation of a conductive polymer pattern in accordance with this methoddoes not require the coating and patterning of a separate photoresistlayer.

U.S. Pat. No. 6,045,977 describes a process for patterning conductivepolyaniline layers containing a photobase generator. W exposure of suchlayers produces a base that reduces the conductivity in the exposedareas.

EP-A-1 054 414 describes a method to pattern a conductive polymer layerby printing an electrode pattern onto said conductive polymer layerusing a printing solution containing an oxidant selected from the groupClO⁻, BrO⁻, MnO₄ ⁻, Cr₂O₇ ⁻², S₂O₈ ⁻², and H₂O₂. The areas of theconductive layer exposed to the oxidant solution are renderednonconductive.

Research Disclosure, November 1998, page 1473 (disclosure no. 41548)describes various means to form patterns in a conducting polymer,including photoablation wherein the selected areas are removed from thesubstrate by laser irradiation. Such photoablation processes areconvenient dry, one-step methods but the generation of debris mayrequire a wet cleaning step and may contaminate the optics and mechanicsof the laser device. Prior art methods involving removal of theelectroconductive polymer to form the electrode pattern also induce adifference of the optical density between electroconductive andnon-conductive areas of the patterned surface.

Methods of patterning organic electroconductive polymer layers byimage-wise heating by means of a laser have been disclosed in EP 1 079397 A1. That method induces about a 10 to 1000 fold decrease inresistivity without substantially ablating or destroying the layer.

The application of electronically conductive polymers in display relateddevices has been envisioned in the past. European Patent ApplicationEP9910201 describes a light transmissive substrate having a lighttransmissive conductive polymer coating for use in resistive touchscreens. U.S. Pat. No. 5,738,934 describes touch screen cover sheetshaving a conductive polymer coating.

U.S. Pat. Nos. 5,828,432 and 5,976,284 describe conductive polymerlayers employed in liquid crystal display devices. The exampleconductive layers are highly conductive but typically have transparencyof 60% or less.

Use of polythiophene as transparent field spreading layers in displayscomprising polymer dispersed liquid crystals has been disclosed in U.S.Pat. Nos. 6,639,637 and 6,707,517. However, the polythiophene layers inthese patents are non-conductive in nature.

Use of transparent coating on glass substrates for cathode ray tubesusing polythiophene and silicon oxide composites has been disclosed inU.S. Pat. No. 6,404,120. However, the method suggests in-situpolymerization of an ethylenedioxythiohene monomer on glass, baking itat an elevated temperature and subsequent washing with tetra ethylorthosilicate. Such an involved process may be difficult to practice forroll-to-roll production of a wide flexible plastic substrate.

Use of in-situ polymerized polythiophene and polypyrrole has beenproposed in U.S. Pat Appl. Pub. 2003/0008135 A1 as conductive films, forITO replacement. As mentioned earlier, such processes are difficult toimplement for roll-to-roll production of conductive coatings. In thesame patent application, a comparative example was created using adispersion of poly (3,4 ethylene dioxythiophene)/polystyrene sulfonicacid which resulted in inferior coating properties.

Use of commercial polythiophene coated sheet such as Orgacon from Agfahas been suggested for manufacturing of thin film inorganic lightemitting diode has been suggested in U.S. Pat. No. 6,737,293. However,the transparency vs. surface electrical resistivity of such products maynot be sufficient for some applications.

Although there is considerable art describing various methods to formand pattern electronically conductive polymers, there are someapplications where it may be difficult or impractical to involve any wetprocessing or cumbersome patterning steps. For example, wet processingduring coating and/or patterning may adversely affect integrity,interfacial characteristics, and/or electrical or optical properties ofthe previously deposited layers. Additionally, the device manufacturermay not have coating facilities to handle large quantity of liquid. Itis conceivable that many potentially advantageous device constructions,designs, layouts, and materials are impractical because of thelimitations of conventional wet coating and patterning. There is a needfor new methods of forming these devices with a reduced number ofprocessing steps, particularly wet processing steps. In at least someinstances, this may allow for the construction of devices with morereliability and more complexity.

Use of thermal transfer elements and thermal transfer methods forforming multicomponent devices have been proposed previously. Forexample, Wolk et al. in a series of patents (e.g., U.S. Pat. Nos.6,114,088; 6,140,009; 6,214,520; 6,221,553; 6,582,876; 6,586,153)disclose thermal transfer elements and methods, for multilayer devices.However, such elements are non-transparent, often including alight-to-heat conversion layer, interlayer, release layer and the like.Construction of such multilayered elements are complex, involved andprone to defects that can get incorporated into the final device. Elliset al. (U.S. Pat. No. 5,171,650) and Blanchet-Fincher (U.S. Pat. Appl.Pub. 2004/0065970 A1) describe ablative laser thermal transfer ofconductive layers. However, such methods are prone to creating dirt anddebris that may not be tolerated for many display applications.

PROBLEM TO BE SOLVED

Thus, there is still a need in the art for a suitable transfer elementand a transfer method to form conductive layers, especially thosecomprising electronically conductive polymers on receiver substrates,and incorporating such receivers in electronic and/or optical devices.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a donor laminate fortransfer of an electronically conductive layer to a receiver element.

It is another object to provide methods to transfer an electronicallyconductive layer to a receiver element.

It is still another object to provide methods to transfer anelectronically conductive layer to a receiver element in an electrodepattern.

These and other objects of the invention are accomplished by a donorlaminate for transfer of a conductive polymer comprising a substratehaving thereon a conductive layer comprising at least one electronicallyconductive polymer and a polyanion, in contact with said substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional representation of a donor laminate of theinvention.

FIG. 2 shows a cross-sectional representation of a donor laminate of theinvention comprising a substrate, a conductive layer, and two otherlayers disposed on the conductive layer.

FIG. 3 shows a schematic of a display component formed by the methods ofthe invention comprising a receiver element having a conductive layerconnected to a power source by an electric lead.

FIG. 4 shows a schematic of a polymer dispersed LC display formed by themethods of the invention.

FIG. 5 shows a schematic of an OLED based display formed by the methodsof the invention.

FIG. 6 shows a schematic of a resistive-type touch screen formed by themethods of the invention.

FIG. 7 shows a cross-sectional representation of a donor laminate of theinvention and a receiver element.

FIG. 8 shows a cross-sectional representation of a donor laminate of theinvention in contact with a receiver element, as per Example TM-1.

FIG. 9 shows a cross-sectional representation of a receiver elementhaving a conductive layer that has been transferred by the methods ofthe invention.

FIG. 10 shows a cross-sectional representation of a display devicedescribed in Example TM-1.

ADVANTAGEOUS EFFECT OF THE INVENTION

The invention provides a desirable transfer element and a transfermethod to form conductive layers, especially those comprisingelectronically conductive polymers on receiver substrates, andincorporating such receivers in electronic and/or optical devices.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the present invention relates to donor laminates and methodsof using donor laminates for forming devices.

More particularly, the present invention is directed to a laminate fortransfer of a conductive polymer comprising a substrate having thereon aconductive layer comprising an electronically conductive polymer and apolyanion, in contact with said substrate. Optionally, the laminatefurther comprises one or more other layers disposed on the conductivelayer that include operational layers and auxiliary layers of a device.

Another embodiment is a method of transferring a conductive layer to areceiver to form a device, including contacting a receiver with a donorlaminate having a substrate and a conductive layer comprising anelectronically conductive polymer and a polyanion. The present inventionis applicable to the formation or partial formation of devices and otherobjects using various transfer mechanisms and donor laminateconfigurations for forming the devices or other objects.

The donor laminates of the invention can be used to form, for example,electronic circuitry, resistors, capacitors, diodes, rectifiers,electroluminescent lamps, memory elements, field effect transistors,bipolar transistors, unijunction transistors, MOS transistors,metal-insulator-semiconductor transistors, charge coupled devices,insulator-metal-insulator stacks, organic conductor-metal-organicconductor stacks, integrated circuits, photodetectors, lasers, lenses,waveguides, gratings, holographic elements, filters (e.g., add-dropfilters, gain-flattening filters, cut-off filters, and the like),mirrors, splitters, couplers, combiners, modulators, sensors (e.g.,evanescent sensors, phase modulation sensors, interferometric sensors,and the like), optical cavities, piezoelectric devices, ferroelectricdevices, thin film batteries, or combinations thereof; for example, thecombination of field effect transistors and organic electroluminescentlamps as an active matrix array for an optical display.

Preferred embodiments are donor laminates for forming a polymerdispersed LC display, an OLED based display, or a resistive-type touchscreen. The donor laminates include a substrate, a conductive layer, andone or more other layers that are configured and arranged to form, upontransfer to a receiver, at least two operational layers of the device.The present invention also includes a polymer dispersed LC display, anOLED based display, a resistive-type touch screen, or other electronicor optical device formed using the donor laminate.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

The term, “device”, includes an electronic or optical component that canbe used by itself and/or with other components to form a larger system,such as an electronic circuit.

The term, “active device”, includes an electronic or optical componentcapable of a dynamic function, such as amplification, oscillation, orsignal control, and may require a power supply for operation.

The term, “passive device”, includes an electronic or optical componentthat is basically static in operation (i.e., it is ordinarily incapableof amplification or oscillation) and may require no power forcharacteristic operation.

The term, “operational layer” includes layers that are utilized in theoperation of device, such as a multilayer active or passive device.Examples of operational layers include layers that act as insulating,conducting, semiconducting, superconducting, waveguiding, frequencymultiplying, light producing (e.g., luminescing, light emitting,fluorescing or phosphorescing), electron producing, hole producing,magnetic, light absorbing, reflecting, diffracting, phase retarding,scattering, dispersing, refracting, polarizing, or diffusing layers inthe device and/or layers that produce an optical or electronic gain inthe device.

The term, “auxiliary layer” includes layers that do not perform afunction in the operation of the device, but are provided solely, forexample, to facilitate transfer of a layer to a receiver element, toprotect layers of the device from damage and/or contact with outsideelements, and/or to adhere the transferred layer to the receiverelement.

Turning now to FIG. 1 there is presented a cross-sectionalrepresentation of a donor laminate 14 comprising a substrate 12 havingthereon a conductive layer 10 comprising an electronically conductivepolymer and a polyanion, in contact with said substrate 12.

The substrate 12 can be transparent, translucent or opaque, rigid orflexible, and may be colored or colorless. Preferred substrates aretransparent. Rigid substrates can include glass, metal, ceramic and/orsemiconductors. Flexible substrates, especially those comprising aplastic substrate, are preferred for their versatility and ease ofmanufacturing, coating and finishing. Flexible plastic substrates can beany flexible self-supporting plastic film that supports the conductivelayer. “Plastic” means a high polymer, usually made from polymericsynthetic resins, which may be combined with other ingredients, such ascuratives, fillers, reinforcing agents, colorants, and plasticizers.Plastic includes thermoplastic materials and thermosetting materials.

The flexible plastic substrate has sufficient thickness and mechanicalintegrity so as to be self-supporting, yet should not be so thick as tobe rigid. Another significant characteristic of the flexible plasticsubstrate material is its glass transition temperature (Tg). Tg isdefined as the glass transition temperature at which plastic materialwill change from the glassy state to the rubbery state. It may comprisea range before the material may actually flow. Suitable materials forthe flexible plastic substrate include thermoplastics of a relativelylow glass transition temperature, for example up to 150° C., as well asmaterials of a higher glass transition temperature, for example, above150° C. The choice of material for the flexible plastic substrate woulddepend on factors such as manufacturing process conditions, such asdeposition temperature, and annealing temperature, as well aspost-manufacturing conditions such as in a process line of a displaysmanufacturer. Certain of the plastic substrates discussed below canwithstand higher processing temperatures of up to at least about 200°C., some up to 300°-350° C., without damage.

Although the substrate can be transparent, translucent or opaque, formost applications, transparent substrate(s) are preferred. Althoughvarious examples of plastic substrates are set forth below, it should beappreciated that the flexible substrate can also be formed from othermaterials such as flexible glass and ceramic.

Typically, the flexible plastic substrate is a polyester includingpolyethylene terephthalate (PET), polyethylene naphthalate (PEN),polyester ionomer, polyethersulfone (PES), polycarbonate (PC),polysulfone, a phenolic resin, an epoxy resin, polyester, polyimide,polyetherester, polyetheramide, cellulose nitrate, cellulose acetate,poly(vinyl acetate), polystyrene, polyolefins including polyolefinionomers, polyamide, aliphatic polyurethanes, polyacrylonitrile,polytetrafluoroethylenes, polyvinylidene fluorides, poly(methyl(x-methacrylates), an aliphatic or cyclic polyolefin, polyarylate (PAR),polyetherimide (PEI), polyethersulphone (PES), polyimide (PD, Teflonpolyperfluoro-alboxy) fluoropolymer (PFA), poly(ether ether ketone)(PEEK), poly(ether ketone) (PEK), poly(ethylenetetrafluoroethylene)fluoropolymer (PETFE), and poly(methyl methacrylate)and various acrylate/methacrylate copolymers (PMMA) natural andsynthetic paper, resin-coated or laminated paper, voided polymersincluding polymeric foam, microvoided polymers and microporousmaterials, or fabric, or any combinations thereof. Aliphatic polyolefinsmay include high density polyethylene (HDPE), low density polyethylene(LDPE), and polypropylene, including oriented polypropylene (OPP).

The preferred flexible plastic donor substrates are polyester andcellulose acetate because of their superior mechanical and thermalproperties as well as their availability in large quantity at a moderateprice.

Most preferred cellulose acetate for use as the donor substrate iscellulose triacetate, also known as triacetylcellulose or TAC. TAC filmhas traditionally been used by the photographic industry due to itsunique physical properties, and flame retardance. TAC film is also thepreferred polymer film for use as a cover sheet for polarizers used inliquid crystal displays.

The manufacture of TAC films by a casting process is well known andincludes the following process. A TAC solution in organic solvent (dope)is typically cast on a drum or a band, and the solvent is evaporated toform a film. Before casting the dope, the concentration of the dope istypically so adjusted that the solid content of the dope is in the rangeof 18 to 35 wt. %. The surface of the drum or band is typically polishedto give a mirror plane. The casting and drying stages of the solventcast methods are described in U.S. Pat. Nos. 2,336,310, 2,367,603,2,492,078, 2,492,977, 2,492,978, 2,607,704, 2,739,069, 2,739,070,British Patent Nos. 640,731, 736,892, Japanese Patent Publication Nos.45(1970)-4554, 49(1974)-5614, Japanese Patent Provisional PublicationNos. 60(1985)-176834, 60(1985)-203430 and 62(1987)-115035.

A plasticizer can be added to the cellulose acetate film to improve themechanical strength of the film. The plasticizer has another function ofshortening the time for the drying process. Phosphoric esters andcarboxylic esters (such as phthalic esters and citric esters) areusually used as the plasticizer. Examples of the phosphoric estersinclude triphenyl phosphate (TPP) and tricresyl phosphate (TCP).Examples of the phthalic esters include dimethyl phthalate (DMP),diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate(DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP).Examples of the citric esters include o-acetyltriethyl citrate (OACTE)and o-acetyltributyl citrate (OACTB). The amount of the plasticizer isin the range of typically 0.1 to 25 wt. %, conveniently 1 to 20 wt. %,desirably 3 to 15 wt. % based on the amount of cellulose acetate.

The particular polyester chosen for use as the donor substrate can be ahomo-polyester or a co-polyester, or mixtures thereof as desired. Thepolyester can be crystalline or amorphous or mixtures thereof asdesired. Polyesters are normally prepared by the condensation of anorganic dicarboxylic acid and an organic diol and, therefore,illustrative examples of useful polyesters will be described hereinbelow in terms of these diol and dicarboxylic acid precursors.

Preferred polyesters for use in the donor for the practice of thisinvention include poly(ethylene terephthalate), poly(butyleneterephthalate), poly(1,4-cyclohexylene dimethylene terephthalate) andpoly(ethylene naphthalate) and copolymers and/or mixtures thereof. Amongthese polyesters of choice, poly(ethylene terephthalate) is mostpreferred.

The aforesaid substrate can be planar and/or curved. The curvature ofthe substrate can be characterized by a radius of curvature, which mayhave any value. Alternatively, the substrate may be bent so as to forman angle. This angle may be any angle from 0° to 360°, including allangles therebetween and all ranges therebetween. The substrate may be ofany thickness, such as, for example. 10⁻⁸ cm to 1 cm including allvalues in between. The preferred thickness of the substrate variesbetween 1 to 200 μm, to optimize physical properties and cost. Thesubstrate need not have a uniform thickness. The preferred shape issquare or rectangular, although any shape may be used. Before thesubstrate 12 is coated with the conductive layer 10 it may be physicallyand/or optically patterned, for example by rubbing, by the applicationof an image, by the application of patterned electrical contact areas,by the presence of one or more colors in distinct regions, by embossing,microembossing, microreplication, etc.

The aforesaid substrate can comprise a single layer or multiple layersaccording to need. The multiplicity of layers may include any number ofadditional layers such as antistatic layers, tie layers or adhesionpromoting layers, abrasion resistant layers, curl control layers,conveyance layers, barrier layers, splice providing layers, UV, visibleand/or infrared light absorption layers, optical effect providinglayers, such as antireflective and antiglare layers, waterproofinglayers, adhesive layers, release layers, magnetic layers, interlayers,imageable layers and the like.

In one preferred embodiment, the substrate comprises a release layer onthe surface of the substrate that is in contact with the conductivelayer. The release layer facilitates separation of the conductive layerfrom the substrate during the transfer process. Suitable materials foruse in the release layer include, for example, polymeric materials suchas polyvinylbutyrals, cellulosics, polyacrylates, polycarbonates andpoly(acryloritrile-co-vinylidene chloride-co-acrylic acid). The choiceof materials used in the release layer may be optimized empirically bythose skilled in the art.

The polymer substrate can be formed by any method known in the art suchas those involving extrusion, coextrusion, quenching, orientation, heatsetting, lamination, coating and solvent casting. The substrate can bean oriented sheet formed by any suitable method known in the art, suchas by a flat sheet process or a bubble or tubular process. The flatsheet process involves extruding or coextruding the materials of thesheet through a slit die and rapidly quenching the extruded orcoextruded web upon a chilled casting drum so that the polymericcomponent(s) of the sheet are quenched below their solidificationtemperature. Alternatively, the sheet can be formed by casting asolution of the sheet material on a drum or band and evaporating thesolvent.

The sheet thus formed is then oriented by stretching uniaxially orbiaxially in mutually perpendicular directions at a temperature abovethe glass transition temperature of the polymer(s). The sheet may bestretched in one direction and then in a second direction or may besimultaneously stretched in both directions. The preferred stretch ratioin any direction is at least 3:1. After the sheet has been stretched, itcan be heat set by heating to a temperature sufficient to crystallizethe polymers while restraining to some degree the sheet againstretraction in both directions of stretching.

The substrate polymer sheet may be subjected to any number of coatingsand treatments, after casting, extrusion, coextrusion, orientation, etc.or between casting and fill orientation, to improve and/or optimize itsproperties, such as printability, barrier properties, heat-sealability,spliceability, adhesion to other substrates and/or imaging layers.Examples of such coatings can be acrylic coatings for printability,polyvinylidene halide for heat seal properties, etc. Examples of suchtreatments can be flame, plasma and corona discharge treatment,ultraviolet radiation treatment, ozone treatment, electron beamtreatment, acid treatment, alkali treatment, saponification treatment toimprove and/or optimize any property, such as coatability and adhesion.Further examples of treatments can be calendaring, embossing andpatterning to obtain specific effects on the surface of the web. Thepolymer sheet can be further incorporated in any other suitablesubstrate by coating, lamination, adhesion, cold or heat sealing,extrusion, co-extrusion, or any other method known in the art.

The conductive layer of the invention can comprise any of the knownelectronically conductive polymers, such as substituted or unsubstitutedpyrrole-containing polymers (as mentioned in U.S. Pat. Nos. 5,665,498and 5,674,654), substituted or unsubstituted thiophene-containingpolymers (as mentioned in U.S. Pat. Nos. 5,300,575, 5,312,681,5,354,613, 5,370,981, 5,372,924, 5,391,472, 5,403,467, 5,443,944,5,575,898, 4,987,042, and 4,731,408) and substituted or unsubstitutedaniline-containing polymers (as mentioned in U.S. Pat. Nos. 5,716,550,5,093,439, and 4,070,189). However, particularly suitable are those,which comprise an electronically conductive polymer in its cationic formand a polyanion, since such a combination can be formulated in aqueousmedium and hence environmentally desirable. Examples of such polymersare disclosed in U.S. Pat. Nos. 5,665,498 and 5,674,654 forpyrrole-containing polymers and U.S. Pat. No. 5,300,575 forthiophene-containing polymers. Among these, the thiophene-containingpolymers are most preferred because of their light and heat stability,dispersion stability and ease of storage and handling.

Preparation of the Aforementioned Thiophene Based Polymers has beendiscussed in detail in a publication titled“Poly(3,4-ethylenedioxythiophene) and its derivatives: past, present andfuture” by L. B. Groenendaal, F. Jonas, D. Freitag, H. Pielartzik and J.R. Reynolds in Advanced Materials, (2000), 12, No. 7, pp. 481-494, andreferences therein.

In a preferred embodiment, the layer containing the electronicallyconductive polymer is prepared by applying a mixture comprising:

a) a polythiophene according to Formula I

in a cationic form, wherein each of R1 and R2 independently representshydrogen or a C1-4 alkyl group or together represent an optionallysubstituted C1-4 alkylene group or a cycloalkylene group, preferably anethylene group, an optionally alkyl-substituted methylene group, anoptionally C1-12 alkyl- or phenyl-substituted 1,2-ethylene group, a1,3-propylene group or a 1,2-cyclohexylene group; and n is 3 to 1000;

and

b) a polyanion compound;

It is preferred that the electronically conductive polymer and polyanioncombination is soluble or dispersible in organic solvents or water ormixtures thereof. For environmental reasons, aqueous systems arepreferred. Polyanions used with these electronically conductive polymersinclude the anions of polymeric carboxylic acids such as polyacrylicacids, poly(methacrylic acid), and polymaleic acid), and polymericsulfonic acids such as polystyrenesulfonic acids and polyvinylsulfonicacids, the polymeric sulfonic acids being preferred for use in thisinvention because of its stability and availability in large scale.These polycarboxylic and polysulfonic acids may also be copolymersformed from vinylcarboxylic and vinylsulfonic acid monomerscopolymerized with other polymerizable monomers such as the esters ofacrylic acid and styrene. The molecular weight of the polyacidsproviding the polyanions preferably is 1,000 to 2,000,000 and morepreferably 2,000 to 500,000. The polyacids or their alkali salts arecommonly available, for example as polystyrenesulfonic acids andpolyacrylic acids, or they may be produced using known methods. Insteadof the free acids required for the formation of the electricallyconducting polymers and polyanions, mixtures of alkali salts ofpolyacids and appropriate amounts of monoacids may also be used. Thepolythiophene to polyanion weight ratio can widely vary between 1:99 to99:1, however, optimum properties such as high electrical conductivityand dispersion stability and coatability are obtained between 85:15 and15:85, and more preferably between 50:50 and 15:85. The most preferredelectronically conductive polymers include poly(3,4-ethylenedioxythiophene styrene sulfonate) which comprises poly(3,4-ethylenedioxythiophene) in a cationic form and polystyrenesulfonic acid.

Desirable results such as enhanced conductivity of the conductive layercan be accomplished by incorporating a conductivity enhancing agent(CEA). Preferred CEAs are organic compounds containing dihydroxy,poly-hydroxy, carboxyl, amide, or lactam groups, such as

(1) those represented by the following Formula II:(OH)_(n)—R—(COX)_(m)  II

wherein m and n are independently an integer of from 1 to 20, R is analkylene group having 2 to 20 carbon atoms, an arylene group having 6 to14 carbon atoms in the arylene chain, a pyran group, or a furan group,and X is —OH or —NYZ, wherein Y and Z are independently hydrogen or analkyl group; or

(2) a sugar, sugar derivative, polyalkylene glycol, or glycerolcompound; or

(3) those selected from the group consisting of N-methylpyrrolidone,pyrrolidone, caprolactam, N-methyl caprolactam, dimethyl sulfoxide orN-octylpyrrolidone; or

(4) a combination of the above.

Particularly preferred conductivity enhancing agents are: sugar andsugar derivatives such as sucrose, glucose, fructose, lactose; sugaralcohols such as sorbitol, mannitol; furan derivatives such as2-furancarboxylic acid, 3-furancarboxylic acid; alcohols such asethylene glycol, glycerol, di- or triethylene glycol. Most preferredconductivity enhancing agents are ethylene glycol, glycerol, di- ortriethylene glycol, as they provide maximum conductivity enhancement.

The CEA can be incorporated by any suitable method. Preferably the CEAis added to the coating composition comprising the electronicallyconductive polymer and the polyanion. Alternatively, the coated anddried conductive layer can be exposed to the CEA by any suitable method,such as a post-coating wash.

The concentration of the CEA in the coating composition may vary widelydepending on the particular organic compound used and the conductivityrequirements. However, convenient concentrations that may be effectivelyemployed in the practice of the present invention are about 0.5 to about25 weight %; more conveniently 0.5 to 10 and more desirably 0.5 to 5.

The conductive layer of the invention can be formed by any method knownin the art. Particularly preferred methods include coating from asuitable coating composition by any well known coating method such asair knife coating, gravure coating, hopper coating, curtain coating,roller coating, spray coating, electrochemical coating, inkjet printing,flexographic printing, stamping, and the like.

While the conductive layer can be formed without the addition of afilm-forming polymeric binder, a film-forming binder can be employed toimprove the physical properties of the layer. In such an embodiment, thelayer may comprise from about 1 to 95% of the film-forming polymericbinder. However, the presence of the film forming binder may increasethe overall surface electrical resistivity of the layer. The optimumweight percent of the film-forming polymer binder varies depending onthe electrical properties of the electronically conductive polymer, thechemical composition of the polymeric binder, and the requirements forthe particular circuit application.

Polymeric film-forming binders useful in the conductive layer of thisinvention can include, but are not limited to, water-soluble orwater-dispersible hydrophilic polymers such as gelatin, gelatinderivatives, maleic acid or maleic anhydride copolymers, polystyrenesulfonates, cellulose derivatives (such as carboxymethyl cellulose,hydroxyethyl cellulose, cellulose acetate butyrate, diacetyl cellulose,and triacetyl cellulose), polyethylene oxide, polyvinyl alcohol, andpoly-N-vinylpyrrolidone. Other suitable binders include aqueousemulsions of addition-type homopolymers and copolymers prepared fromethylenically unsaturated monomers such as acrylates including acrylicacid, methacrylates including methacrylic acid, acrylamides andmethacrylamides, itaconic acid and its half-esters and diesters,styrenes including substituted styrenes, acrylonitrile andmethacrylonitrile, vinyl acetates, vinyl ethers, vinyl and vinylidenehalides, and olefins and aqueous dispersions of polyurethanes andpolyesterionomers.

Other ingredients that may be included in the conductive layer includebut are not limited to surfactants, defoamers or coating aids, chargecontrol agents, thickeners or viscosity modifiers, antiblocking agents,coalescing aids, crosslinking agents or hardeners, soluble and/or solidparticle dyes, matte beads, inorganic or polymeric particles, adhesionpromoting agents, bite solvents or chemical etchants, lubricants,plasticizers, antioxidants, colorants or tints, and other addenda thatare well-known in the art. Preferred bite solvents can include any ofthe volatile aromatic compounds disclosed in U.S. Pat. No. 5,709,984, as“conductivity-increasing” aromatic compounds, comprising an aromaticring substituted with at least one hydroxy group or a hydroxysubstituted substituents group. These compounds include phenol,4-chloro-3-methyl phenol, 4-chlorophenol, 2-cyanophenol,2,6-dichlorophenol, 2-ethylphenol, resorcinol, benzyl alcohol,3-phenyl-1-propanol, 4-methoxyphenol, 1,2-catechol,2,4-dihydroxytoluene, 4-chloro-2-methyl phenol, 2,4-dinitrophenol,4-chlororesorcinol, 1-naphthol, 1,3-naphthalenediol and the like. Thesebite solvents are particularly suitable for polyester based polymersheets of the invention. Of this group, the most preferred compounds areresorcinol and 4-chloro-3-methyl phenol. Preferred surfactants suitablefor these coatings include nonionic and anionic surfactants. Preferredcross-linking agents suitable for these coatings include silanecompounds, more preferably epoxy silane. Suitable silane compounds aredisclosed in U.S. Pat. No. 5,370,981.

The conductive layer of the invention should contain about 1 to about1000 mg/m² dry coating weight of the electronically conductive polymer.Preferably, the conductive layer should contain about 5 to about 500mg/m² dry coating weight of the electronically conductive polymer. Theactual dry coating weight of the conductive polymer applied isdetermined by the properties of the particular conductive polymeremployed and by the requirements of the particular application. Theserequirements include conductivity, transparency, optical density andcost for the layer.

For some specific display applications, such as those involving organicor polymeric light emitting diodes the surface roughness of theconductive layer can be critical. Typically, a very smooth surface, withlow roughness (Ra, roughness average) is desired for maximizing opticaland barrier properties of the coated substrate. Preferred Ra values forthe conductive layer of the invention, particularly after its transferto a receiver, is less than 1000 nm, more preferably less than 100 nm,and most preferably less than 20 nm. However, it is to be understoodthat if for some application a rougher surface is required higher Ravalues can be attained within the scope of this invention, by any meansknown in the art

A key criterion of the conductive layer of the invention involves twoimportant characteristics: transparency and surface electricalresistance. The stringent requirement of high transparency and low SERdemanded by modern display devices can be extremely difficult to attainwith electronically conductive polymers. Typically, lower surfaceelectrical resistance values are obtained by coating relatively thicklayers which undesirably reduces transparency. Additionally, even thesame general class of conductive polymers, such as polythiophenecontaining polymers, may result in different SER and transparencycharacteristics, based on differences in molecular weight, impuritycontent, doping level, morphology and the like.

It is found during the course of this invention that a figure of merit(FOM) can be assigned to the conductive layer. Such FOM values aredetermined by (1) measuring the visual light transmission (T) and thesurface electrical resistance (SER) of the conductive layer at variousthickness values of the layer, (2) plotting these data in a ln (1/T) vs.1/SER space, and (3) then determining the slope of a straight line bestfitting these data points and passing through the origin of such a plot.It is found that ln (1/T) vs. 1/SER plots for electronically conductivepolymer layers, particularly those comprising polythiophene in acationic form with a polyanion compound, generate a linear relationship,preferably one passing through the origin, wherein the slope of such alinear plot is the FOM of the electronically conductive polymer layer.It is also found that lower the FOM value, more desirable is theelectrical and optical characteristics of the electronically conductivepolymer layer; namely, lower the FOM, lower is the SER and higher is thetransparency of the conductive layer. For the instant invention,electronically conductive polymer layers of FOM values<150, preferably≦100, and more preferably ≦50 are most desired, particularly for displayapplications.

Visual light transmission value T is determined from the total opticaldensity at 530 nm, after correcting for the contributions of theuncoated substrate. A Model 361T X-Rite densitometer measuring totaloptical density at 530 nm, is best suited for this measurement.

Visual light transmission, T, is related to the corrected total opticaldensity at 530 nm, o.d.(corrected), by the following expression,T=1/(10^(o.d.(corrected)))

The SER value is typically determined by a standard four-pointelectrical probe.

The SER value of the electronically conductive polymer layer of theinvention can vary according to need. For use as an electrode in adisplay device, the SER is typically less than 10000 ohms/square,preferably less than 5000 ohms/square, and more preferably less than1000 ohms/square and most preferably less than 500 ohms/square, as perthe current invention.

The transparency of the conductive layer of the invention can varyaccording to need. For use as an electrode in a display device, theconductive layer is desired to be highly transparent. Accordingly, thevisual light transmission value T for the conductive layer of theinvention is preferably ≧65%, more preferably ≧80%, and most preferably≧90%.

The conductive layer need not form an integral whole, need not have auniform thickness and need not be continuous. However, in accordancewith the invention, the conductive layer is contiguous to the substrateof the donor laminate.

Turning now to FIG. 2 which shows a cross-sectional representation of adonor laminate 28 of the invention comprising a substrate 26, aconductive layer 20, and two other layers 22 and 24 disposed on theconductive layer 20. Layers 22 and 24 can be any combination ofoperational layers or auxiliary layers. Examples of operational layersinclude layers that act as dielectric, conducting, semiconducting,superconducting, waveguiding, frequency multiplying, imageable, lightproducing (e.g., luminescing, light emitting, fluorescing orphosphorescing), electron producing, hole producing, magnetic, lightabsorbing, reflecting, diffracting, phase retarding, scattering,dispersing, refracting, polarizing, or diffusing layers in the deviceand/or layers that produce an optical or electronic gain in the device.

Auxiliary layers include layers that do not perform a function in theoperation of the device, but are provided solely, for example, tofacilitate transfer of a layer to a receiver element, to protect layersof the device from damage and/or contact with outside elements, and/orto adhere the transferred layer to the receiver element. Specificexamples of auxiliary layers include: antistatic layers, tie layers oradhesion promoting layers, abrasion resistant layers, curl controllayers, conveyance layers, barrier layers, splice providing layers, UV,visible and/or infrared light absorption layers, optical effectproviding layers, such as antireflective and antiglare layers,waterproofing layers, adhesive layers, magnetic layers, interlayers andthe like.

In the donor laminate illustrated in FIG. 2, for example, layer 22 couldbe a dielectric layer and layer 24 could be an adhesive layer thatfacilitates the transfer of conductive layer 20 and dielectric layer 22to a receiver element.

It should be obvious to one skilled in the art that a wide variety ofdonor laminate configurations employing various combinations ofoperational layers and auxiliary layers may be constructed depending onthe type of device that is being constructed and the transfer meansbeing employed.

An active or passive device can be formed, at least in part, by thetransfer of at least a conductive layer from a donor laminate comprisinga substrate and conductive layer comprising an electronically conductivepolymer and a polyanion, in contact with said substrate, by bringing theside of said laminate bearing said conductive layer into contact with areceiver element, applying heat, pressure, or heat and pressure, andseparating the said substrate from the receiver element. In at leastsome instances, pressure or vacuum are used to hold the transferlaminate in intimate contact with the receiver element.

The donor laminate can be heated by application of directed heat on aselected portion of the donor laminate. Heat can be generated using aheating element (e.g., a resistive heating element), convertingradiation (e.g., a beam of light) to heat, and/or applying an electricalcurrent to a layer of the donor laminate to generate heat. In manyinstances, thermal transfer using light from, for example, a lamp orlaser, is advantageous because of the accuracy and precision that canoften be achieved. The size and shape of the transferred pattern (apattern is defined as an arrangement of lines and shapes, e.g., a line,circle, square, or other shape) can be controlled by, for example,selecting the size of the light beam, the exposure pattern of the lightbeam, the duration of directed beam contact with the donor laminate, andthe materials of the thermal transfer element.

Suitable lasers include, for example, high power (>100 mW) single modelaser diodes, fiber-coupled laser diodes, and diode-pumped solid statelasers (e.g., Nd:YAG and Nd:YLF). Laser exposure dwell times can be inthe range from, for example, about 0.1 to 100 microseconds and laserfluences can be in the range from, for example, about 0.01 to about 1J/cm².

When high spot placement accuracy is required (e.g. for high informationfull color display applications) over large substrate areas, a laser isparticularly useful as the radiation source. Laser sources arecompatible with both large rigid substrates such as 1 m×m×1.1 mm glass,and continuous or sheeted film substrates, such as 100 μm polyimidesheets.

For laser transfer, the donor laminate is typically brought intointimate contact with a receiver. In at least some instances, pressureor vacuum are used to hold the donor laminate in intimate contact withthe receiver. A laser source is then used in an imagewise fashion (e.g.,digitally or by analog exposure through a mask) to perform imagewisetransfer of materials from the donor laminate to the receiver accordingto any pattern. In operation, a laser can be rastered or otherwise movedacross the donor laminate and the receiver, the laser being selectivelyoperated to illuminate portions of the donor laminate according to adesired pattern. Alternatively, the laser may be stationary and thedonor laminate and receiver moved beneath the laser.

Unlike prior art (e.g. U.S. Patent Nos. U.S. Pat. Nos. 6,114,088;6,140,009; 6,214,520; 6,221,553; 6,582,876; 6,586,153), the presentinvention does not require a separate light-to-heat conversion layer.Such a layer typically reduces light transmission and may not bedesirable for many applications. Nevertheless, in some applications thelight-to-heat layer may be utilized.

Alternatively, a heating element, such as a resistive heating element,may be used to affect the transfer. Typically, the donor laminate isselectively contacted with the heating element to cause thermal transferof at least the conductive layer according to a pattern. In anotherembodiment, the donor laminate may include a layer that can convert anelectrical current applied to the donor into heat.

Resistive thermal print heads or arrays may be particularly useful withsmaller substrate sizes (e.g., less than approximately 30 cm in anydimension) or for larger patterns, such as those required foralphanumeric segmented displays.

Pressure can be applied during the transfer operation using eithermechanically or acoustically generated force. Mechanical force may begenerated by a variety of means well known in the art, for example, bycontacting the donor laminate and receiver element between opposing niprollers. The nip rollers may be smooth or one or both rollers may havean embossed pattern. Alternatively, the mechanical force may begenerated by the action of a stylus upon either the donor laminate orreceiver element when they are in intimate contact. The donor andreceiver may be contacted in a stamping press using either smooth orpatterned platens. Another means of applying mechanical force includethe use of acoustic force. Acoustic force may be generated using adevice similar to that disclosed in U.S. Patent Application Publication2001/0018851 wherein a transducer passes acoustic energy through anacoustic lens which in turn focuses its received acoustic energy into asmall focal area of the donor laminate when it is in intimate contactwith the receiver element.

Peel force for separation of the conductive layer from the donorlaminate substrate is an important consideration as that plays a role inthe transfer process. Peel force for separation of the conductive layerfrom the donor laminate substrate is determined using an IMASS SP-2000Peel Tester. In this testing, the conductive layer on the donor laminatesubstrate is lightly scored with a razor knife. A 2 inch wide Permaceltape is next applied with a 5 lb roller over the sample, over the razorknife cut. Strips of 1 inch×6 inch of the sample and tape composite thusprepared, are next subjected to a 180° peel force. The tape is peeledback at 180° with the conductive layer bonded to it, at 12 ft/min usinga 5 kilograms load cell in the IMASS SP-2000 Peel Tester. The averagepeel force measured in g/inch is reported as the peel force forseparation of the conductive layer from the donor laminate substrate.

For the purpose of the invention, it is preferred that the peel forcefor separation of the conductive layer from the donor laminate substrateis <100 g/inch, more preferably, <50 g/inch, at room temperature and/orat the transfer temperature, the temperature at which the conductivelayer is transferred from the donor laminate to the receiver. Dependingon the choice of substrate for the donor laminate and the receiver andthe method of transfer, it is also desirable that the peel force forseparation of the conductive layer from the donor laminate substrate is<100 g/inch, more preferably, <50 g/inch, at elevated temperatures up to300° C.

To facilitate the transfer process, the surface of the donor laminate incontact with the receiver element may be an adhesive layer.Alternatively, the surface of the receiver element in contact with adonor laminate may be an adhesive layer. The adhesive layer may be apressure sensitive adhesive layer comprising a low Tg polymer, a heatactivated adhesive layer comprising a thermoplastic polymer, or athermally or radiation curable adhesive layer. Examples of suitablepolymers for use in the adhesive layer include acrylic polymers,styrenic polymers, polyolefins, polyurethanes, and other polymers wellknown in the adhesives industry.

The donor laminates and transfer process of the invention is useful, forexample, to reduce or eliminate wet processing steps of processes suchas photolithographic patterning which is used to form many electronicand optical devices. In addition, laser thermal transfer can oftenprovide better accuracy and quality control for very small devices, suchas small optical and electronic devices, including, for example,transistors and other components of integrated circuits, as well ascomponents for use in a display, such as electroluminescent lamps andcontrol circuitry. Moreover, laser thermal transfer may, at least insome instances, provide for better registration when forming multipledevices over an area that is large compared to the device size. As anexample, components of a display, which has many pixels, can be formedusing this method.

In some instances, multiple donor laminates may be used to form a deviceor other object. The multiple donor laminates may include donorlaminates having two or more layers and donor laminates that transfer asingle layer.

For example, one donor laminate may be used to form a gate electrode ofa field effect transistor and another donor laminate may be used to formthe gate insulating layer and semiconducting layer, and yet anotherdonor laminate may be used to form the source and drain contacts. Avariety of other combinations of two or more donor laminates can be usedto form a device, each donor laminates forming one or more layers of thedevice.

The receiver substrate may be any substrate described herein above forthe donor laminate substrate. Suitable items for a particularapplication include, but not limited to, transparent films, displayblack matrices, passive and active portions of electronic displays,metals, semiconductors, glass, various papers, and plastics.Non-limiting examples of receiver substrates which can be used in thepresent invention include anodized aluminum and other metals, plasticfilms (e.g., polyethylene terephthalate, polypropylene), indium tinoxide coated plastic films, glass, indium tin oxide coated glass,flexible circuitry, circuit boards, silicon or other semiconductors, anda variety of different types of paper (e.g., filled or unfilled,calendered, or coated), textile, woven or non-woven polymers. Variouslayers (e.g., an adhesive layer) may be coated onto the receiversubstrate to facilitate transfer of the transfer layer to the receiversubstrate. Other layers may be coated on the receiver substrate to forma portion of a multilayer device.

In a particularly preferred embodiment, the receiver substrate forms atleast a portion of a device, most preferably a display device. Thedisplay device typically comprises at least one imageable layer whereinthe imageable layer can contain an electrically imageable material. Theelectrically imageable material can be light emitting or lightmodulating. Light emitting materials can be inorganic or organic innature. Particularly preferred are organic light emitting diodes (OLED)or polymeric light emitting diodes (PLED). The light modulating materialcan be reflective or transmissive. Light modulating materials can beelectrochemical, electrophoretic, such as Gyricon particles,electrochromic, or liquid crystals. The liquid crystalline material canbe twisted nematic (TN), super-twisted nematic (STN), ferroelectric,magnetic, or chiral nematic liquid crystals. Especially preferred arechiral nematic liquid crystals. The chiral nematic liquid crystals canbe polymer dispersed liquid crystals (PDLC). Structures having stackedimaging layers or multiple substrate layers, however, are optional forproviding additional advantages in some case.

After transferring the conductive layer and any other operational orauxiliary layers, the conductive layer may simply be incorporated in adevice as any one or more conducting electrodes present in such priorart devices. In some such cases the conductive layer preferably has atleast one electric lead attached to (in contact with) it for theapplication of current, voltage, etc. (i.e. electrically connected). Thelead(s) is/are preferably not in electrical contact with the substrateand may be made of patterned deposited metal, conductive orsemiconductive material, such as ITO, may be a simple wire in contactwith the conducting polymer, and/or conductive paint comprising, forexample, a conductive polymer, carbon, and/or metal particles. Devicesaccording to the invention preferably also include a current or avoltage source electrically connected to the conducting electrodethrough the lead(s). A power source, battery, etc. may be used. Oneembodiment of the invention is illustrated in FIG. 3 as a displaycomponent 60, wherein an electronically conductive polymer layer 64 hasbeen transferred, as per invention, from a donor (not shown) on to areceiver substrate 62, and is connected to a power source 66 by means ofan electric lead 68. In addition to or alternative to functioning as anelectrode, the transfer layer of the invention can form any otheroperational and/or non-operational layer in any device.

In a preferred embodiment, the electrically imageable material can beaddressed with an electric field and then retain its image after theelectric field is removed, a property typically referred to as“bistable”. Particularly suitable electrically imageable materials thatexhibit “bistability” are electrochemical, electrophoretic, such asGyricon particles, electrochromic, magnetic, or chiral nematic liquidcrystals. Especially preferred are chiral nematic liquid crystals. Thechiral nematic liquid crystals can be polymer dispersed liquid crystals(PDLC).

For purpose of illustration of the application of the present invention,the display will be described primarily as a liquid crystal display.However, it is envisioned that the present invention may find utility ina number of other display applications.

As used herein, a “liquid crystal display” (LCD) is a type of flat paneldisplay used in various electronic devices. At a minimum, an LCDcomprises a substrate, at least one conductive layer and a liquidcrystal layer. LCDs may also comprise two sheets of polarizing materialwith a liquid crystal solution between the polarizing sheets. The sheetsof polarizing material may comprise a substrate of glass or transparentplastic. The LCD may also include functional layers. In one embodimentof an LCD item 50, illustrated in FIG. 4, a transparent, multilayerflexible substrate 54 has a first conductive layer 52, which may bepatterned, onto which is coated the light-modulating liquid crystallayer 48. A second conductive layer 40 is applied and overcoated with adielectric layer 42 to which dielectric conductive row contacts 44 areattached, including vias (not shown) that permit interconnection betweenconductive layers and the dielectric conductive row contacts. Anoptional nanopigmented layer 46 is applied between the liquid crystallayer 48 and the second conductive layer 40. In a typical matrix-addresslight-emitting display device, numerous light-emitting devices areformed on a single substrate and arranged in groups in a regular gridpattern. Activation may be by rows and columns.

The liquid crystal (LC) is used as an optical switch. The substrates areusually manufactured with transparent, conductive electrodes, in whichelectrical “driving” signals are coupled. The driving signals induce anelectric field which can cause a phase change or state change in the LCmaterial, the LC exhibiting different light-reflecting characteristicsaccording to its phase and/or state.

LC

Liquid crystals can be nematic (N), chiral nematic (N*), or smectic,depending upon the arrangement of the molecules in the mesophase. Chiralnematic liquid crystal (N*LC) displays are typically reflective, thatis, no backlight is needed, and can function without the use ofpolarizing films or a color filter.

Chiral nematic liquid crystal refers to the type of liquid crystalhaving finer pitch than that of twisted nematic and super-twistednematic used in commonly encountered LC devices. Chiral nematic liquidcrystals are so named because such liquid crystal formulations arecommonly obtained by adding chiral agents to host nematic liquidcrystals. Chiral nematic liquid crystals may be used to producebi-stable or multi-stable displays. These devices have significantlyreduced power consumption due to their non-volatile “memory”characteristic. Since such displays do not require a continuous drivingcircuit to maintain an image, they consume significantly reduced power.Chiral nematic displays are bistable in the absence of a field; the twostable textures are the reflective planar texture and the weaklyscattering focal conic texture. In the planar texture, the helical axesof the chiral nematic liquid crystal molecules are substantiallyperpendicular to the substrate upon which the liquid crystal isdisposed. In the focal conic state the helical axes of the liquidcrystal molecules are generally randomly oriented. Adjusting theconcentration of chiral dopants in the chiral nematic material modulatesthe pitch length of the mesophase and, thus, the wavelength of radiationreflected. Chiral nematic materials that reflect infrared radiation andultraviolet have been used for purposes of scientific study. Commercialdisplays are most often fabricated from chiral nematic materials thatreflect visible light. Some known LCD devices include chemically-etched,transparent, conductive layers overlying a glass substrate as describedin U.S. Pat. No. 5,667,853, incorporated herein by reference.

In one embodiment, a chiral-nematic liquid crystal composition may bedispersed in a continuous matrix. Such materials are referred to as“polymer-dispersed liquid crystal” materials or “PDLC” materials. Suchmaterials can be made by a variety of methods. For example, Doane et al.(Applied Physics Letters, 48, 269 (1986)) disclose a PDLC comprisingapproximately 0.4 μm droplets of nematic liquid crystal 5CB in a polymerbinder. A phase separation method is used for preparing the PDLC. Asolution containing monomer and liquid crystal is filled in a displaycell and the material is then polymerized. Upon polymerization theliquid crystal becomes immiscible and nucleates to form droplets. Westet al. (Applied Physics Letters 63, 1471 (1993)) disclose a PDLCcomprising a chiral nematic mixture in a polymer binder. Once again aphase separation method is used for preparing the PDLC. Theliquid-crystal material and polymer (a hydroxy functionalizedpolymethylmethacrylate) along with a cross-linker for the polymer aredissolved in a common organic solvent toluene and coated on atransparent conductive layer on a substrate. A dispersion of theliquid-crystal material in the polymer binder is formed upon evaporationof toluene at high temperature. The phase separation methods of Doane etal. and West et al. require the use of organic solvents that may beobjectionable in certain manufacturing environments.

The contrast of the display is degraded if there is more than asubstantial monolayer of N*LC domains. The term “substantial monolayer”is defined by the Applicants to mean that, in a direction perpendicularto the plane of the display, there is no more than a single layer ofdomains sandwiched between the electrodes at most points of the display(or the imaging layer), preferably at 75 percent or more of the points(or area) of the display, most preferably at 90 percent or more of thepoints (or area) of the display. In other words, at most, only a minorportion (preferably less than 10 percent) of the points (or area) of thedisplay has more than a single domain (two or more domains) between theelectrodes in a direction perpendicular to the plane of the display,compared to the amount of points (or area) of the display at which thereis only a single domain between the electrodes.

The amount of material needed for a monolayer can be accuratelydetermined by calculation based on individual domain size, assuming afully closed packed arrangement of domains. (In practice, there may beimperfections in which gaps occur and some unevenness due to overlappingdroplets or domains.) On this basis, the calculated amount is preferablyless than about 150 percent of the amount needed for monolayer domaincoverage, preferably not more than about 125 percent of the amountneeded for a monolayer domain coverage, more preferably not more than110 percent of the amount needed for a monolayer of domains.Furthermore, improved viewing angle and broadband features may beobtained by appropriate choice of differently doped domains based on thegeometry of the coated droplet and the Bragg reflection condition.

In a preferred embodiment of the invention, the display device ordisplay sheet has simply a single imaging layer of liquid crystalmaterial along a line perpendicular to the face of the display,preferably a single layer coated on a flexible substrate. Such asstructure, as compared to vertically stacked imaging layers each betweenopposing substrates, is especially advantageous for monochrome shelflabels and the like. Structures having stacked imaging layers, however,are optional for providing additional advantages in some case.

Preferably, the domains are flattened spheres and have on average athickness substantially less than their length, preferably at least 50%less. More preferably, the domains on average have a thickness (depth)to length ratio of 1:2 to 1:6. The flattening of the domains can beachieved by proper formulation and sufficiently rapid drying of thecoating. The domains preferably have an average diameter of 2 to 30microns. The imaging layer preferably has a thickness of 10 to 150microns when first coated and 2 to 20 microns when dried. The flatteneddomains of liquid crystal material can be defined as having a major axisand a minor axis. In a preferred embodiment of a display or displaysheet, the major axis is larger in size than the cell (or imaging layer)thickness for a majority of the domains. Such a dimensional relationshipis shown in U.S. Pat. No. 6,061,107.

Modern chiral nematic liquid crystal materials usually include at leastone nematic host combined with a chiral dopant. In general, the nematicliquid crystal phase is composed of one or more mesogenic componentscombined to provide useful composite properties. Many such materials areavailable commercially. The nematic component of the chiral nematicliquid crystal mixture may be comprised of any suitable nematic liquidcrystal mixture or composition having appropriate liquid crystalcharacteristics. Nematic liquid crystals suitable for use in the presentinvention are preferably composed of compounds of low molecular weightselected from nematic or nematogenic substances, for example from theknown classes of the azoxybenzenes, benzylideneanilines, biphenyls,terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl estersof cyclohexanecarboxylic acid; phenyl or cyclohexyl esters ofcyclohexylbenzoic acid; phenyl or cyclohexyl esters ofcyclohexylcyclohexanecarboxylic acid; cyclohexylphenyl esters of benzoicacid, of cyclohexanecarboxylic acid and ofcyclohexylcyclohexanecarboxylic acid; phenyl cyclohexanes;cyclohexylbiphenyls; phenyl cyclohexylcyclohexanes;cyclohexylcyclohexanes; cyclohexylcyclohexenes;cyclohexylcyclohexylcyclohexenes; 1,4-bis-cyclohexylbenzenes;4,4-bis-cyclohexylbiphenyls; phenyl- or cyclohexylpyrimidines; phenyl-or cyclohexylpyridines; phenyl- or cyclohexylpyridazines; phenyl- orcyclohexyldioxanes; phenyl- or cyclohexyl-1,3-dithianes;1,2-diphenylethanes; 1,2-dicyclohexylethanes;1-phenyl-2-cyclohexylethanes;1-cyclohexyl-2-(4-phenylcyclohexyl)ethanes;1-cyclohexyl-2′,2-biphenylethanes; 1-phenyl-2-cyclohexylphenylethanes;optionally halogenated stilbenes; benzyl phenyl ethers; tolanes;substituted cinnamic acids and esters; and further classes of nematic ornematogenic substances. The 1,4-phenylene groups in these compounds mayalso be laterally mono- or difluorinated. The liquid crystallinematerial of this preferred embodiment is based on the achiral compoundsof this type. The most important compounds, that are possible ascomponents of these liquid crystalline materials, can be characterizedby the following formula R′—X—Y—Z—R″ wherein X and Z, which may beidentical or different, are in each case, independently from oneanother, a bivalent radical from the group formed by -Phe-, -Cyc-,-Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -B-Phe- and -B-Cyc-;wherein Phe is unsubstituted or fluorine-substituted 1,4-phenylene, Cycis trans-1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr ispyrimidine-2,5-diyl or pyridine-2,5-diyl, Dio is 1,3-dioxane-2,5-diyl,and B is 2-(trans-1,4-cyclohexyl)ethyl, pyrimidine-2,5-diyl,pyridine-2,5-diyl or 1,3-dioxane-2,5-diyl. Y in these compounds isselected from the following bivalent groups —CH═CH—, —C≡C—, —N═N(O)—,—CH═CY′—, —CH—N(O)—, —CH2-CH2-, —CO—O—, —CH2-O—, —CO—S—, —CH2-S—,—COO-Phe-COO— or a single bond, with Y′ being halogen, preferablychlorine, or —CN; R′ and R″ are, in each case, independently of oneanother, alkyl, alkenyl, alkoxy, alkenyloxy, alkanoyloxy, alkoxycarbonylor alkoxycarbonyloxy with 1 to 18, preferably 1 to 12 C atoms, oralternatively one of R′ and R″ is —F, —CF3, —OCF3, —Cl, —NCS or —CN. Inmost of these compounds R′ and R′ are, in each case, independently ofeach another, alkyl, alkenyl or alkoxy with different chain length,wherein the sum of C atoms in nematic media generally is between 2 and9, preferably between 2 and 7. The nematic liquid crystal phasestypically consist of 2 to 20, preferably 2 to 15 components. The abovelist of materials is not intended to be exhaustive or limiting. Thelists disclose a variety of representative materials suitable for use ormixtures, which comprise the active element in electro-optic liquidcrystal compositions.

Suitable chiral nematic liquid crystal compositions preferably have apositive dielectric anisotropy and include chiral material in an amounteffective to form focal conic and twisted planar textures. Chiralnematic liquid crystal materials are preferred because of theirexcellent reflective characteristics, bi-stability and gray scalememory. The chiral nematic liquid crystal is typically a mixture ofnematic liquid crystal and chiral material in an amount sufficient toproduce the desired pitch length. Suitable commercial nematic liquidcrystals include, for example, E7, E44, E48, E31, E80, BL087, BL101,ZLI-3308, ZLI-3273, ZLI-5048-000, ZLI-5049-100, ZLI-5100-100,ZLI-5800-000, MLC-6041-100.TL202, TL203, TL204 and TL205 manufactured byE. Merck (Darmstadt, Germany). Although nematic liquid crystals havingpositive dielectric anisotropy, and especially cyanobiphenyls, arepreferred, virtually any nematic liquid crystal known in the art,including those having negative dielectric anisotropy should be suitablefor use in the invention. Other nematic materials may also be suitablefor use in the present invention as would be appreciated by thoseskilled in the art.

The chiral dopant added to the nematic mixture to induce the helicaltwisting of the mesophase, thereby allowing reflection of visible light,can be of any useful structural class. The choice of dopant depends uponseveral characteristics including among others its chemicalcompatibility with the nematic host, helical twisting power, temperaturesensitivity, and light fastness. Many chiral dopant classes are known inthe art: e.g., G. Gottarelli and G. Spada, Mol. Cryst. Liq. Crys., 123,377 (1985); G. Spada and G. Proni, Enantiomer, 3, 301 (1998) andreferences therein. Typical well-known dopant classes include1,1-binaphthol derivatives; isosorbide (D-1) and similar isomannideesters as disclosed in U.S. Pat. No. 6,217,792; TADDOL derivatives (D-2)as disclosed in U.S. Pat. No. 6,099,751; and the pending spiroindanesesters (D-3) as disclosed in U.S. patent application Ser. No. 10/651,692by T. Welter et al., filed Aug. 29, 2003, titled “Chiral Compounds AndCompositions Containing The Same,” hereby incorporated by reference.

The pitch length of the liquid crystal materials may be adjusted basedupon the following equation (1):λmax=nav p0where λmax is the peak reflection wavelength, that is, the wavelength atwhich reflectance is a maximum, nav is the average index of refractionof the liquid crystal material, and p0 is the natural pitch length ofthe chiral nematic helix. Definitions of chiral nematic helix and pitchlength and methods of its measurement, are known to those skilled in theart such as can be found in the book, Blinov, L. M., Electro-optical andMagneto-Optical Properties of Liquid Crystals, John Wiley & Sons Ltd.1983. The pitch length is modified by adjusting the concentration of thechiral material in the liquid crystal material. For most concentrationsof chiral dopants, the pitch length induced by the dopant is inverselyproportional to the concentration of the dopant. The proportionalityconstant is given by the following equation (2):p0=1/(HTP.c)

where c is the concentration of the chiral dopant and HTP (as termed □in some references) is the proportionality constant.

For some applications, it is desired to have LC mixtures that exhibit astrong helical twist and thereby a short pitch length. For example inliquid crystalline mixtures that are used in selectively reflectingchiral nematic displays, the pitch has to be selected such that themaximum of the wavelength reflected by the chiral nematic helix is inthe range of visible light. Other possible applications are polymerfilms with a chiral liquid crystalline phase for optical elements, suchas chiral nematic broadband polarizers, filter arrays, or chiral liquidcrystalline retardation films. Among these are active and passiveoptical elements or color filters and liquid crystal displays, forexample STN, TN, AMD-TN, temperature compensation, polymer free orpolymer stabilized chiral nematic texture (PFCT, PSCT) displays.Possible display industry applications include ultralight, flexible, andinexpensive displays for notebook and desktop computers, instrumentpanels, video game machines, videophones, mobile phones, hand-held PCs,PDAs, e-books, camcorders, satellite navigation systems, store andsupermarket pricing systems, highway signs, informational displays,smart cards, toys, and other electronic devices.

There are alternative display technologies to LCDs that may be used, forexample, in flat panel displays. A notable example is organic or polymerlight emitting devices (OLEDs) or (PLEDs), which are comprised ofseveral layers in which one of the layers is comprised of an organicmaterial that can be made to electroluminesce by applying a voltageacross the device. An OLED device is typically a laminate formed in asubstrate such as glass or a plastic polymer. Alternatively, a pluralityof these OLED devices may be assembled such to form a solid statelighting display device.

A light emitting layer of a luminescent organic solid, as well asadjacent semiconductor layers, are sandwiched between an anode and acathode. The semiconductor layers may be hole injecting and electroninjecting layers. PLEDs may be considered a subspecies of OLEDs in whichthe luminescent organic material is a polymer. The light emitting layersmay be selected from any of a multitude of light emitting organicsolids, e.g., polymers that are suitably fluorescent or chemiluminescentorganic compounds. Such compounds and polymers include metal ion saltsof 8-hydroxyquinolate, trivalent metal quinolate complexes, trivalentmetal bridged quinolate complexes, Schiff-based divalent metalcomplexes, tin (IV) metal complexes, metal acetylacetonate complexes,metal bidenate ligand complexes incorporating organic ligands, such as2-picolylketones, 2-quinaldylketones, or 2-(o-phenoxy)pyridine ketones,bisphosphonates, divalent metal maleonitriledithiolate complexes,molecular charge transfer complexes, rare earth mixed chelates,(5-hydroxy)quinoxaline metal complexes, aluminum tris-quinolates, andpolymers such as poly(p-phenylenevinylene),poly(dialkoxyphenylenevinylene), poly(thiophene), poly(fluorene),poly(phenylene), poly(phenylacetylene), poly(aniline),poly(3-alkylthiophene), poly(3-octylthiophene), andpoly(N-vinylcarbazole). When a potential difference is applied acrossthe cathode and anode, electrons from the electron injecting layer andholes from the hole injecting layer are injected into the light emittinglayer; they recombine, emitting light. OLEDs and PLEDs are described inthe following United States patents: U.S. Pat. No. 5,707,745 to Forrestet al., U.S. Pat. No. 5,721,160 to Forrest et al., U.S. Pat. No.5,757,026 to Forrest et al., U.S. Pat. No. 5,834,893 to Bulovic et al.,U.S. Pat. No. 5,861,219 to Thompson et al., U.S. Pat. No. 5,904,916 toTang et al., U.S. Pat. No. 5,986,401 to Thompson et al., U.S. Pat. No.5,998,803 to Forrest et al., U.S. Pat. No. 6,013,538 to Burrows et al.,U.S. Pat. No. 6,046,543 to Bulovic et al., U.S. Pat. No. 6,048,573 toTang et al., U.S. Pat. No. 6,048,630 to Burrows et al., U.S. Pat. No.6,066,357 to Tang et al., U.S. Pat. No. 6,125,226 to Forrest et al.,U.S. Pat. No. 6,137,223 to Hung et al., U.S. Pat. No. 6,242,115 toThompson et al., and U.S. Pat. No. 6,274,980 to Burrows et al.

In a typical matrix address light emitting display device, numerouslight emitting devices are formed on a single substrate and arranged ingroups in a regular grid pattern. Activation may be by rows and columns,or in an active matrix with individual cathode and anode paths. OLEDsare often manufactured by first depositing a transparent electrode onthe substrate, and patterning the same into electrode portions. Theorganic layer(s) is then deposited over the transparent electrode. Ametallic electrode may be formed over the organic layers. For example,in U.S. Pat. No. 5,703,436 to Forrest et al., incorporated herein byreference, transparent indium tin oxide (ITO) is used as the holeinjecting electrode, and a Mg—Ag—ITO electrode layer is used forelectron injection.

The present invention can be employed in most OLED device configurationsas an electrode, preferably as an anode, and/or any other operational ornon-operational layer. These include very simple structures comprising asingle anode and cathode to more complex devices, such as passive matrixdisplays comprised of orthogonal arrays of anodes and cathodes to formpixels, and active-matrix displays where each pixel is controlledindependently, for example, with thin film transistors (TFTs).

There are numerous configurations of the organic layers wherein thepresent invention can be successfully practiced. A typical structure isshown in FIG. 5 and is comprised of a substrate 101, an anode 103, ahole-injecting layer 105, a hole-transporting layer 107, alight-emitting layer 109, an electron-transporting layer 111, and acathode 113. These layers are described in more detail below. Note thatthe substrate may alternatively be located adjacent to the cathode, orthe substrate may actually constitute the anode or cathode. The organiclayers between the anode and cathode are conveniently referred to as theorganic electroluminescent (EL) element. The total combined thickness ofthe organic layers is preferably less than 500 nm.

The anode and cathode of the OLED are connected to a voltage/currentsource 250 through electrical conductors 260. The OLED is operated byapplying a potential between the anode and cathode such that the anodeis at a more positive potential than the cathode. Holes are injectedinto the organic EL element from the anode and electrons are injectedinto the organic EL element at the anode. Enhanced device stability cansometimes be achieved when the OLED is operated in an AC mode where, forsome time period in the cycle, the potential bias is reversed and nocurrent flows. An example of an AC driven OLED is described in U.S. Pat.No. 5,552,678.

When EL emission is viewed through anode 103, the anode should betransparent or substantially transparent to the emission of interest.Thus, the FOM of this invention is critical for such OLED displaydevices. Common transparent anode materials used in this invention areindium-tin oxide (ITO), indium-zinc oxide (IZO) and tin oxide, but othermetal oxides can work including, but not limited to, aluminum- orindium-doped zinc oxide, magnesium-indium oxide, and nickel-tungstenoxide. In addition to these oxides, metal nitrides, such as galliumnitride, and metal selenides, such as zinc selenide, and metal sulfides,such as zinc sulfide, can be used as the anode. For applications whereEL emission is viewed only through the cathode electrode, thetransmissive characteristics of anode are generally immaterial and anyconductive material can be used, transparent, opaque or reflective.Example conductors for this application include, but are not limited to,gold, iridium, molybdenum, palladium, and platinum. Typical anodematerials, transmissive or otherwise, have a work function of 4.1 eV orgreater. Desired anode materials are commonly deposited by any suitablemeans such as evaporation, sputtering, chemical vapor deposition, orelectrochemical means. Anodes can be patterned using well-knownphotolithographic processes. Optionally, anodes may be polished prior toapplication of other layers to reduce surface roughness so as tominimize shorts or enhance reflectivity.

The electrically imageable material may also be a printable, conductiveink having an arrangement of particles or microscopic containers ormicrocapsules. Each microcapsule contains an electrophoretic compositionof a fluid, such as a dielectric or emulsion fluid, and a suspension ofcolored or charged particles or colloidal material. The diameter of themicrocapsules typically ranges from about 30 to about 300 microns.According to one practice, the particles visually contrast with thedielectric fluid. According to another example, the electricallymodulated material may include rotatable balls that can rotate to exposea different colored surface area, and which can migrate between aforward viewing position and/or a rear nonviewing position, such asgyricon. Specifically, gyricon is a material comprised of twistingrotating elements contained in liquid filled spherical cavities andembedded in an elastomer medium. The rotating elements may be made toexhibit changes in optical properties by the imposition of an externalelectric field. Upon application of an electric field of a givenpolarity, one segment of a rotating element rotates toward, and isvisible by an observer of the display. Application of an electric fieldof opposite polarity, causes the element to rotate and expose a second,different segment to the observer. A gyricon display maintains a givenconfiguration until an electric field is actively applied to the displayassembly. Gyricon particles typically have a diameter of about 100microns. Gyricon materials are disclosed in U.S. Pat. Nos. 6,147,791,4,126,854 and 6,055,091, the contents of which are herein incorporatedby reference.

According to one practice, the microcapsules may be filled withelectrically charged white particles in a black or colored dye. Examplesof electrically modulated material and methods of fabricating assembliescapable of controlling or effecting the orientation of the ink suitablefor use with the present invention are set forth in International PatentApplication Publication Number WO 98/41899, International PatentApplication Publication Number WO 98/19208, International PatentApplication Publication Number WO 98/03896, and International PatentApplication Publication Number WO 98/41898, the contents of which areherein incorporated by reference.

The electrically imageable material may also include material disclosedin U.S. Pat. No. 6,025,896, the contents of which are incorporatedherein by reference. This material comprises charged particles in aliquid dispersion medium encapsulated in a large number ofmicrocapsules. The charged particles can have different types of colorand charge polarity. For example white positively charged particles canbe employed along with black negatively charged particles. The describedmicrocapsules are disposed between a pair of electrodes, such that adesired image is formed and displayed by the material by varying thedispersion state of the charged particles. The dispersion state of thecharged particles is varied through a controlled electric field appliedto the electrically modulated material. According to a preferredembodiment, the particle diameters of the microcapsules are betweenabout 5 microns and about 200 microns, and the particle diameters of thecharged particles are between about one-thousandth and one-fifth thesize of the particle diameters of the microcapsules.

Further, the electrically imageable material may include a thermochromicmaterial. A thermochromic material is capable of changing its statealternately between transparent and opaque upon the application of heat.In this manner, a thermochromic imaging material develops images throughthe application of heat at specific pixel locations in order to form animage. The thermochromic imaging material retains a particular imageuntil heat is again applied to the material. Since the rewritablematerial is transparent, UV fluorescent printings, designs and patternsunderneath can be seen through.

The electrically imageable material may also include surface stabilizedferrroelectric liquid crystals (SSFLC). Surface stabilized ferroelectricliquid crystals confining ferroelectric liquid crystal material betweenclosely spaced glass plates to suppress the natural helix configurationof the crystals. The cells switch rapidly between two opticallydistinct, stable states simply by alternating the sign of an appliedelectric field.

Magnetic particles suspended in an emulsion comprise an additionalimaging material suitable for use with the present invention.Application of a magnetic force alters pixels formed with the magneticparticles in order to create, update or change human and/or machinereadable indicia. Those skilled in the art will recognize that a varietyof bistable nonvolatile imaging materials are available and may beimplemented in the present invention.

The electrically imageable material may also be configured as a singlecolor, such as black, white or clear, and may be fluorescent,iridescent, bioluminescent, incandescent, ultraviolet, infrared, or mayinclude a wavelength specific radiation absorbing or emitting material.There may be multiple layers of electrically imageable material.Different layers or regions of the electrically imageable materialdisplay material may have different properties or colors. Moreover, thecharacteristics of the various layers may be different from each other.For example, one layer can be used to view or display information in thevisible light range, while a second layer responds to or emitsultraviolet light. The nonvisible layers may alternatively beconstructed of non-electrically modulated material based materials thathave the previously listed radiation absorbing or emittingcharacteristics. The electrically imageable material employed inconnection with the present invention preferably has the characteristicthat it does not require power to maintain display of indicia.

Another application of the invention is envisioned for touch screens.Touch screens are widely used in conventional CRTs and in flat-paneldisplay devices in computers and in particular with portable computers.The present invention can be applied as a transparent conductive memberin any of the touch screens known in the art, including but not limitedto those disclosed in U.S. Pat. Appl. Pub. 2003/0170456 A1; 2003/0170492A1; U.S. Pat. No. 5,738,934; and WO 00/39835.

FIG. 6 shows a multilayered item 70 for a typical prior artresistive-type touch screen including a transparent substrate 72, havinga first conductive layer 74. A flexible transparent cover sheet 76includes a second conductive layer 78 that is physically separated fromthe first conductive layer 74 by spacer elements 80. A voltage isdeveloped across the conductive layers. The conductive layers 74 and 78have a resistance selected to optimize power usage and position sensingaccuracy. Deformation of the flexible cover sheet 76 by an externalobject such as a finger or stylus causes the second conductive layer 78to make electrical contact with first conductive layer 74, therebytransferring a voltage between the conductive layers. The magnitude ofthis voltage is measured through connectors (not shown) connected tometal conductive patterns (not shown) formed on the edges of conductivelayers 78 and 74 to locate the position of the deforming object.

The conventional construction of a resistive touch screen involves thesequential placement of materials upon the substrate. The substrate 72and cover sheet 76 are first cleaned, then uniform conductive layers areapplied to the substrate and cover sheet. It is known to use a coatableelectronically conductive polymer such as polythiophene or polyanilineto provide the flexible conductive layers. See for example WO 00/39835,which shows a light transmissive substrate having a light transmissiveconductive polymer coating, and U.S. Pat. No. 5,738,934 which shows acover sheet having a conductive polymer coating. The spacer elements 80are then applied and, finally, the flexible cover sheet 76 is attached.

For many applications, specific functional layers in devices may havepatterned structures. For example patterning of color filters, blackmatrix, spacers, polarizers, conductive layers, transistors, phosphors,and organic electroluminescent materials have all been proposed. Inaccordance with the present invention, a patterned structure can beobtained by (i) pre-patterning all or any part of the transfer layerbefore transfer, (ii) patterning all or any part of the transfer layerafter transfer and (iii) pattern-wise transfer of all or any part of thetransfer layer during transfer.

A field effect transistor (FET) can be formed using one or more donorlaminates. One example of an organic field effect transistor that couldbe formed using donor laminates is described in Garnier, et al., Adv.Mater. 2, 592-594 (1990). Similar examples are illustrated in U.S. Pat.No. 6,586,153 and references therein. Any of the known art can beimplemented for the practice of the present invention.

EXAMPLES

Donor Laminates

The following ingredients were used to form the coating composition forforming the donor laminate examples:

Ingredients for Coating Composition

-   (a) Baytron P HC: aqueous dispersion of electronically conductive    polythiophene and polyanion, namely, poly(3,4-ethylene    dioxythiophene styrene sulfonate), supplied by H. C. Starck;-   (b) Olin 10G: nonionic surfactant supplied by Olin Chemicals;-   (c) N-methylpyrrolidone: conductivity enhancing agent supplied by    Acros;-   (d) diethylene glycol: conductivity enhancing agent supplied by    Aldrich;-   (e) Silquest A 187: 3-glycidoxy-propyltrimethyoxysilane supplied by    Crompton Corporation and-   (f) isopropanol;    The following coating composition A was prepared for coating    suitable substrates to form the laminate examples:

Coating composition A Baytron P HC (1.3% aqueous) 88.71 g Olin 10G (10%aqueous) 0.5 g N-methylpyrrolidone 5.16 g Diethylene glycol 4 g SilquestA 187 1.8 g Isopropanol 4.33 gThe laminate substrates used were triacetylcellulose (TAC) andpolyethylene terephthalate (PET). Two different types of TAC substrateswere used: TAC1 was a photographic grade triacetylcellulose with athickness of 127 μm, surface roughness Ra of 1.0 in; TAC2 was an opticalgrade triacetylcellulose with a thickness of 80 μm, surface roughness Raof 0.6 nm; The PET substrate was photographic grade with a thickness of102 μm and surface roughness Ra of 0.5 nm. In all cases the surface ofthe substrate was corona discharge treated prior to coating. The coatingcomposition A was applied to the corona discharge treated surface of thesubstrate by a hopper at different wet lay downs, and each coating wasdried at 82° C. for five minutes. In this manner, examples of donorlaminates DL-1 through DL-6 were created as per invention, whereinconductive layers of different coverage of electronically conductivepolythiophene and polyanions of polystyrenesulfonic acid were coated onthe surface of the substrate.

The surface electrical resistivity (SER) of the coating was measured bya 4-point electrical probe. The peel force for separation of the coatingfrom the substrate was determined using an IMASS SP-2000 Peel Tester, asdescribed herein above. The details of the donor laminates and theirproperties are tabulated below in Table 1.

TABLE 1 Exam- sub- Coating Wet lay SER Peel force ple strate compositiondown cc/ft² ohms/square g/inch DL-1 TAC1 A 3 594 17 DL-2 TAC1 A 2 638 15DL-3 TAC2 A 3 407 12 DL-4 TAC2 A 2 694 13 DL-5 PET A 3 376 20 DL-6 PET A2 552 22

It is very clear that exemplary donor laminates DL-1 through DL-6 allhave SER much less than 1000 ohms/square. In addition, for all theselaminates the peel force for separation of the conductive layer from thesubstrate is significantly <50 g/inch as preferred for the practice ofthe invention.

Donor laminate DL-7 was further created by coating a one μm layer (drythickness) of an adhesive polyester ionomer, AQ 29D, supplied by EastmanChemicals Company, on the conductive layer of donor laminate DL-3, asdescribed herein above.

Receiver

The following receivers were prepared for the transfer of the conductivelayer as per the invention:

R-1: A 120 μm PET substrate, coated with a 0.1 μm layer of sputterdeposited indium tin oxide (ITO) with an SER of 300 ohms/square, furthercoated with a 10 μm imageable layer comprising gelatin and droplets ofcholesteric liquid crystal, contiguous with the said ITO layer.

R-2: A 102 μm PET substrate with an adhesion promoting subbing layer ofa terpolymer of acrylonitrile, vinylidene chloride and acrylic acid inthe weight ratio of 15/79/6 and having a glass transition temperature of42° C.

R-3: glass.

Transfer Methods:

TM-1: Transfer by Heat and Pressure

Donor laminate DL-3 and receiver R-1 are schematically illustrated inFIG. 7. As per FIG. 7A the donor laminate DL-3 consists of a TAC2substrate 90, which is coated with a conductive layer 92 comprisingelectronically conductive polythiophene and polyanions ofpolystyrenesulfonic acid. As per same FIG. 7B, the receiver R-1 consistsof a PET substrate 94, coated with a sputter deposited ITO layer 96,which is further coated with an imageable layer 98 comprising gelatinand droplets of cholesteric liquid crystal.

The donor laminate DL-3 and receiver R-1 were brought in close contactwith each other, with the imageable layer 98 of R-1 touching theconductive layer 92 of DL-3, and were passed through the nip between apair of heated laminating rollers, which exerted pressure and heat tothe combination, as schematically represented in FIG. 8. Upon a singlepass, a composite was created wherein the donor laminate and thereceiver adhered to each other. Next the TAC2 substrate 90 was peeledoff from the composite, as schematically shown in FIG. 9, leaving behindthe conductive layer 92 completely transferred to the imageable layer 98of the receiver.

In this way a single cell display device, was created, as schematicallyillustrated in FIG. 10. The said single cell display device comprised ofthe following components: (a) PET substrate 94, coated with a (b)sputter deposited ITO layer 96, further coated with a (c) an imageablelayer 98 comprising gelatin and droplets of cholesteric liquid crystal(LC), and (d) a conductive layer 92 comprising polythiophene transferredto the imageable layer.

The SER of the transferred conductive layer was measured and was foundto be the same as before the transfer, i.e., the same as the conductivesurface of DL-3 prior to transfer, as noted in Table 1. This indicated acomplete transfer of the conductive layer from the donor laminate to thereceiver. The completeness of the transfer was further verified by X-rayphotoelectron spectroscopy (XPS) measurements of the donor laminatesubstrate. No sulfur peak corresponding to polyethylenedioxythiophene orpolystyrenesulfonic acid was detected by XPS on the peeled surface ofDL-3 after the transfer.

The two conductive layers 96 and 92 (namely, the ITO layer and thetransferred conductive layer comprising polythiophene, respectively) ofthe aforesaid single cell display device, were connected by electricleads 300 to a voltage source 302 as illustrated in FIG. 10. Uponapplication of appropriate voltages, the droplets of cholesteric liquidcrystal in the imageable layer of the display device, were alternatelyswitched between planar and focal conic states, demonstrating afunctioning display device.

In a similar manner as described hereinabove, the following donorlaminate-to-receiver combinations (vide Table 2) were used to transferthe conductive layer comprising polythiophene. In each case the SER ofthe conductive layer comprising polythiophene was found to be the sameboth before and after the transfer.

TABLE 2 Donor laminate Transfer layer Receiver Receiving layer DL-1Conductive polythiophene layer R-1 Imageable layer (LC &gelatin) DL-3Conductive polythiophene layer R-1 Imageable layer (LC &gelatin) DL-5Conductive polythiophene layer R-1 Imageable layer (LC &gelatin) DL-3Conductive polythiophene layer R-2 Adhesion promoting terpolymer layerDL-7 Conductive polythiophene & R-3 glass adhesive polyester ionomerlayer

TM-2: Wet Transfer

The glass surface of receiver R-3 was coated with an aqueous dispersionof AQ 29D (at 10% solids by weight) at a wet coverage of 1 cc/ft². Thedonor laminate DL-3 was placed on this coated surface so that theconductive layer of DL-3 contacted the AQ 29D layer of R-3. Thecombination was allowed to dry for 10 minutes at 80° C. forming acomposite structure. Subsequently the TAC2 substrate was peeled off fromthe composite, leaving the conductive layer completely transferred tothe AQ 29D coated glass receiver.

TM-3: Laser Transfer

The donor laminate DL-3 was placed on Receiver R-1 with the imageablelayer of R-1 touching the conductive layer of DL-3, and the combinationwas kept in close contact with each other using vacuum. Transfer of theconductive layer from the donor element to the substrate was effectedover an area of 1 cm×1 cm by irradiation of the donor element with an830 nm wavelength infrared laser beam. The beam size was approximately16 μm by 80 μm to the 1/e² intensity point. The scanning was parallel tothe wide beam direction. The power dissipation was 610 mw at a scan rateof 10 Hz. At the end of the irradiation, the TAC2 substrate was peeledoff, leaving behind the conductive layer completely transferred to theimageable layer of the receiver over the irradiated 1 cm×1 cm region.

In this way a single cell display device, similar to one created as perTM-1, was formed as per TM-3. The single cell display device as per TM-3comprised of the following components: (a) 120 μm PET substrate, coatedwith a (b) 0.1 μm layer of sputter deposited indium tin oxide (ITO),further coated with a (c) 10 μm layer of an imageable layer comprisinggelatin and droplets of cholesteric liquid crystal (LC), and (d) aconductive layer comprising polythiophene transferred to the imageablelayer. Upon application of appropriate voltages, the droplets ofcholesteric liquid crystal in the imageable layer of this displaydevice, were alternately switched between planar and focal conic states,demonstrating a functioning display device.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

-   10 conductive layer-   12 substrate-   14 donor laminate-   20 conductive layer-   22 dielectric layer-   24 adhesive layer-   26 substrate-   40 second conductive layer-   42 dielectric layer-   44 conductive row contacts-   46 nanopigmented layer-   48 light modulating liquid crystal layer-   50 LCD item-   52 first conductive layer-   54 substrate-   60 display component-   64 conductive polymer layer-   62 receiver substrate-   66 power source-   68 electric lead-   70 resistive touch screen-   72 substrate-   74 first conductive layer-   76 cover sheet-   78 second conductive layer-   80 spacer element-   90 TAC2 substrate-   92 conductive layer-   94 PET substrate-   96 ITO layer-   98 imageable layer-   101 substrate-   103 anode-   105 hole-injecting layer-   107 hole-transporting layer-   109 light-emitting layer-   111 electron-transporting layer-   113 cathode-   250 voltage/current source-   260 electrical conductors-   300 electric lead-   302 voltage source

1. A method of transferring comprising providing a laminate for transferof a conductive layer comprising a substrate having thereon a conductivelayer comprising at least one transparent, electronically conductivepolymer and a polyanion, in contact with said substrate, bringing theside of said laminate bearing said conductive layer into contact with areceiver element to transfer said conductive layer to said receiverelement, wherein the conductive layer has a peel force of less than 100grams per inch for separation from the substrate at room temperature. 2.The method of claim 1 wherein heat is applied during transfer.
 3. Themethod of claim 1 wherein pressure is applied during transfer.
 4. Themethod of claim 1 wherein heat and pressure are applied during transfer.5. The method of claim 2 wherein a light source is utilized to supplyheat during transfer.
 6. The method of claim 2 wherein a resistive headis used to supply heat during transfer.
 7. The method of claim 1 whereinthe receiver element comprises glass.
 8. The method of claim 1 whereinsaid receiver element comprises a flexible polymeric material.
 9. Themethod of claim 1 wherein the transfer is in a pattern for an electrode.10. The method of claim 1 wherein said transfer is in a pattern.
 11. Themethod of claim 1 wherein said receiver element is solvent sensitive.12. The method of claim 1 wherein said receiver element comprises anorganic light emitting diode material.
 13. The method of claim 3 whereinsaid pressure is applied by a patterned roller.
 14. The method of claim3 wherein said pressure is applied by acoustic or mechanical force. 15.The method of claim 1 wherein the surface of said substrate in contactwith said conductive layer comprises a release material.
 16. The methodof claim 1 wherein transferring utilizes an adhesive between saidconductive layer and said receiver element.
 17. The product formed bythe method of claim
 1. 18. The method of claim 5 wherein the lightsource is utilized to supply heat during transfer is a laser.
 19. Themethod of claim 1, wherein said conductive layer has an FOM less than orequal to 100 wherein FOM is defined as the slope of the plot of ln (1/T)versus [1/SER]: and wherein T=visual light transmission SER=surfaceelectrical resistance in ohm per square FOM=figure of merit, and whereinthe SER has a value of less than or equal to 1000 ohm per square.